Imaging With X-Rays

7/25/2019 Imaging With X-Rays

1/107

Imaging with X-RayBy Nipun


2/107

IMAGE QUALITY

WHAT IS IMAGE QUALITY?

Image quality describes the !erall a""eara#ce $ thea#d its ftness or purpose.

There is al%ays a "lay& bet%ee# image quality a#d dse'

S %e al%ays #eed images that are $ diag#stic !alu$r "ur"se #t the !isually a""eali#g "ictures'


3/107

IMAGE QUALITY

The mai# $actrs t c#sider are) *#trast

S"atial +esluti#

,ise

-istrti# .lur


4/107

*/,T+AST

*#trast0 r mre "recisely c#trast resluti#0is the ability t disti#guish bet%ee# ad1ace#tareas $ the image'

S0 better c#trast mea#s better a""reciati# $

The amu#t $ c#trast bet%ee# tissues is i#tri#li#2ed t their "r"erties a#d the imagi#g mdabei#g used'


5/107

*/,T+AST


6/107

+adigra"

hicc#trast)

3ilm

c#trast

Sub1ect

c#trast


7/107

SU.4E*T */,T+AST

A structure i# the "atie#t is dem#strated by t%

Resolution, sharpness0 r lac2 $ blurri#g $ thimage $ its bu#dary'

Contrast bet%ee# it a#d ad1ace#t tissues causedi&ere#ces i# the tra#smissi# $ 56rays 7r atte$ 56+ays8'


8/107

3A*T/+S A33E*TI,G SU.4E*T*/,T+AST

Sub1ect c#trast C de"e#ds #)The thic2#ess t $ the structure'

The di$$ere#ce i# li#ear atte#uati# ce$$icie#ts $ the tissues i#!l!ed %hich is de"e#de#t # thde#sities a#d atmic #'

Thus

C = (1 2) t


9/107


As atte#uati# de"e#ds # tissue de#sity a#d at#umber)

The mre the t% tissues di&er i# these res"ectsgreater the c#trast'

The higher the 2 > the smaller the atte#uati#

ce@cie#ts > the less is the c#trast


10/107


+adiati# quality ) e#etrati#g ability r 2' Mremre is the "e#etrati#g "%er0 less is the c#tra


11/107


12/107


13/107

.ALA,*I,G */,T+AST A,-ATIE,T -/SE

A ma1r c#siderati# i# 56+ay imagi#g is t restrict th$ the "atie#t as much as "ssible des"ite able t "rdsatis$actry image'

e#etrati#0 *#trast a#d atie#t -se de"e#d u"# 5beam s"ectrum0 the best s"ectrum "r!ides adequate

e#etrati# a#d *#trast %hile 2ee"i#g the atie#t -l%est "ssible

The s"ectrum "rduced is de"e#de#t u"# the target i#here#t r added (ltrati# a#d 2il6!ltage'


14/107

.ALA,*I,G */,T+AST A,-ATIE,T -/SE

L% E#ergy 728 B L% e#etrati# B High *#tHigh atie#t -se

High E#ergy 728 B High e#etrati# B L% *#tL% atie#t -se

/"timum Situati# ) 2 that gi!es adequatec#a# acceptable"atie#t dse'


15/107

ATIE,T -/SE

This is abut CGy or ilm screen radiography a

between about 0.2 and 0.5 Gy s-1 or uoroscop

!his is the e"it dose emerging rom the patient.

The e#tra#ce sur$ace dse has t be much highebecause $ high atte#uati# $ 56+ays by the "a


16/107

3ILM */,T+AST

Factors affecting film contrast:

Films vary in inherent contrast depending on- Emulsion characteristics.

Development process.

Time-temperature used in processing.


17/107

/!er eD"sed (lm

U#der eD"sed

MaD'c#trast


18/107

*/,T+AST ME-IA

/#e %ay $ i#creasi#g the c#trast is t use a la#ther is t use a c#trast medium'

A c#trast media is a radi6"aque media %ith hatmic #'

The high atmic #' $ the c#trast maDimiFes t"htelectric absr"ti# $ the 56+ays'


19/107

*/,T+AST ME-IA

The t% cmm# c#trast age#ts are Idi#e 76.arium 768'

Air ca# als be used as c#trast media but #% #ly i# duble c#trast barium e#ema studies'


20/107

*/,+AST A,- S*ATTE+

rimary radiati# carries the i#$rmati# t be im

Scatter bscures it as it carries # i#$rmati# a%here it came $rm'

The amu#t $ scatter 7S8 may be se!eral time tamu#t $ "rimary 78 i# the same "siti#'


21/107

*/,+AST A,- S*ATTE+

The SJ +ati de"e#ds # the thic2#ess $ the "atie#t'

3r ty"ical A *hest it is K); 7


22/107

*/,T+AST A,- S*ATTE+

S*ATTE+ +A-IATI/,result i# 3/GGI,G $image'


23/107

SATIAL +ES/LUTI/,

SATIAL +ES/LUTI/, is the ability t detedetail %ithi# a# image'

3i#e detail is mst clearly see# %he# thec#trast bet%ee# the $eature a#d its bac2is high'


24/107

SATIAL +ES/LUTI/,

S"atial resluti# ca# be qua#ti(ed as the higheccurri#g $reque#cy $ li#es that ca# be resl!edhigh c#trast bar "atter#'

The b1ect used t measure the s"atial resluti

2#%# as #$%& '($) !&*! !++#.


25/107

SATIAL +ES/LUTI/, O LI,E AITEST T//L It uses bars $ lead %ith

%idth $ bar equal t thes"ace bet%ee# them'

A bar a#d s"ace ma2es u"the li#e "air a#d s"atial$reque#cy $ the "atter# is

gi!e# as li#e "air "er mm'

The smallest !isible detail isa""rDimately hal$ $ thei#!erse $ the resluti#eD"ressed i# this %ay


26/107

,/ISE

,/ISE re$ers t the !ariati#s i# the le!els $ greimage that are distributed !er its area but u#rethe structures bei#g imaged'

The mst sig#i(ca#t surce $ #ise i# radilgic

imagi#g is quantum noise or mottle'


27/107

,/ISE

,ise reduces the !isibility $ l% c#trast regi#%ithi# the image0 "articularly i$ they are small i#thus reduci#g the !isibility $ (#er detail i# the i

The l%er the #' $ "ht#s detected0 the great

be the #ise'


28/107

Qua#tum mttle

Audible or visible disturbance that hampers theinformation'


29/107

Quantummottle

Normal


30/107

Lesser for slow screen film than fastscreen film'

Increases with high contrast film asdensity differences are exaggerated

Increases with increase of KV .

QUA,TUM M/TTLE


31/107

ATTE,UATI/, /3 56+AYS .Y THATIE,T

In conventional projection radiography, a $au#i$rm0 $eatureless beam $ 56radiati# $alls #"atie#t > it is di&ere#tially absrbed by the tissuthe bdy > the 56ray beam emergi#g $rm the "carries a "atter# $ i#te#sity %hich is de"e#de#tthickness a#d composition o the organs in th


32/107

ATTE,UATI/, /3 56+AYS .Y THATIE,TThe 56rays emergi#g $rm the "atie#t are ca"turelarge Pat "hs"hr scree# > this c#!erts the i#!ray image i#t a !isible image $ light0 %hich the#either)

+ecrded as a #egati!e image # (lm0 t be !ie%

a light bD 7(lm O scree# radigra"hy8 +ecrded electr#ically "rir t "ri#ti#g 7cm"ut

direct digital radigra"hy8

-is"layed as a "siti!e image # a !ide m#it7Pursc"y8'


33/107

-IST/+TI/,

Distortion

Size Sha


34/107

SiFe 6 Mag#i(cati#

Shrter the dista#ce bet%ee# b1ect a#d the sulight0 greater is the mag#i(cati#'

Surce $light

b1ect

shad%

Surce $ ligh

b1ect


35/107

Law of magnication states that%idth $ the image is t the %idth $the b1ect0 as the dista#ce $ image$rm the light surce is t dista#ce$ the b1ect $rm the light surce

Image width = Image distance !"#ect width !"#ect distance

Li i ti f i


36/107

Linear magnication of imag

Mag#i(cati# $actr) image %idth

6666666666666666666666

b1ect %idth'

Mag#i(cati#) image %idth 6 b1ect %idth

666666666666666666666666666666666

b1ect %idth


37/107

Sha"e distrti#)

It is misalignment ofcentral ray, the anatomic

part and the film.


38/107


39/107

T SummariFe'

Greater distrti# mea#s "rrecrded detail

Sha"e distrti# is due tim"r"er alig#me#t

SiFe distrti#) mag#i(cati# is due tdi!erge#ce $ beam' Shrter the /I- a#d L#ger the SI- O less is the

distrti#'


40/107

Macrradigra"hy

reser!ati# $ recrdeddetail %hile achie!i#g

mag#i(cati#'

3racti#al $cals"tJmicr$cus tubes areusedR %ith small $cal

s"t 7'Cmm8

Principleofradiographic


41/107

Principle of radiographicmagnification

%

o

&!' &

Image

Ideal "i#tsurce


42/107


43/107


44/107

.lur

+eometric"lur

!"#ect "lur

&creen"lur

,otion "lur


45/107

Gemetric .lur 7e#umbra8

Arra#geme#t $ 56+ay0 a#atmical "art a#d (lm s"ace'

-e"e#ds #)

-.ecti/e focal s*ot si0e

&ource to image rece*tor distance

!"#ect to image rece*tor distance


46/107

3cal s"t is larger tha# b1ect

3i#ite

$cal s"t

b1ect

.lur


47/107

E&ecti!e $cal s"t siFe

3cals"t

blu

r

3cal s"t

3cal s"t

blur

A . *


48/107

E&ecti!e $cal s"t

,rmal siFe $ $cal s"t u#derstates the e&ecti!

"r1ected siFe $ the s"t by sig#i(ca#t margi#'

ED) 'C mm $cal s"t may be as large as 'Kmm


49/107

b1 i di


50/107

/b1ect image rece"tr dista#ce

A .

Mti# blur


51/107

Mti# blur

Any motion while taking a radiograph can hampe

image.

b iii db


52/107

It can be minimised by:

ImmbiliFati#$ the "art bysa#dbags rcm"ressi#

ba#ds

Sus"e#si#

$res"irati#

Usi#g sh

eD"sure

S bl


53/107

Scree# blur

Cardboard holders provide better recorded

detail than screen as immobilization ispresent

In uncontrolled motion: fast exposurewith screens is used.

Extremely short exposure using highspeed screen can hamper recorded detail.


54/107

3ilm scree#

cmbi#ati#)

Its a combination of film andintensifying screen.

Recorded details is better in fastspeed and medium speed screen

combination

d d d t il i h ith


55/107

ecorded detail is ne/er shar* withintensifing screen "ecause

*rystalsiFe

Acti!elayer

thic2#es

s

3ilmscree#

c#tact

Q t M ttl


56/107

Qua#tum Mttle

Audible or visible disturbance that hampers inform


57/107

Quantummottle

Normal

/b1ect blur


58/107

/b1ect blur

E&ect $ b1ect blur is greater tha# a""reciated'

/b1ects ha!i#g ru#d brder i#trduce blur $act

/b1ect .lur


59/107

/b1ect .lur

T SummariFe


60/107

T SummariFe'

.lur decreases %ith decrease i# $cal s"t siFe0 /

i#crease i# SI- Mti# blur decreased by immbiliFati# r shr

eD"sure

*ardbard hlders decrease scree# blur

+u#ded b1ects i#crease blur' Quantum mottle$ /isi"ledisturba#ce i# D ray

Less i# sl% scree# rece"trs0 mre i# $ast scree# rec


61/107


62/107

Sil!er halide

Metallic sil!er

A""ears blac2


63/107

Radiographic density depends on:

Amount of radiation reaching a particular area of

film

The resulting mass of metallic silver deposited pe

area

Measureme#t


64/107

Measureme#t

Measured by a# i#strume#t called -E,SIT/METE

Density = log incident light intensity

transmitted light intensity

Clear film: has a density of 0.06-0.2

Diagnostic radiograph: 0.4 in lightest area and 3 in

3actrs A&ecti#g ED"sure a#d


65/107

-e#sityKV: KV- exposure rate- density

Milli ampere: increases exposure rate

Time: increase in exposure time- increases no. of photoemitted by target.

mA.s: measure of charge transferred from cathode to anduring an exposure.


66/107

X-ray photons arise from variouspoint of focal spot.

Assume photons spread in form ofcone from focal spot after leavingtube'

E33E*T /3

-ISTA,*E)

Radiographic exposure rate decreasesas focus film distance increases'


67/107


68/107

+adigra"hic b1ect


69/107

+adigra"hic b1ect

Thic2er a#d de#ser

a#atmical "arts

mre absr"ti# $ Dray'

less eDit $ radiati# #t (lm

/rder $ tissue de#sity


70/107

-e#tal

e#amel

.#eTissu

e3at gas

T summariFe'


71/107

T summariFe'

-e#sity is dar2e#i#g $ D ray (lm due t de"sit

sil!er'

-e"e#ds #6 2!0 mA0 eD"sure time0 dista#ce0 de#sity'

As the dista#ce $ (lm $rm surce i#creases0 eDdecreases'

'-6IC-& %!


72/107

'-6IC-& %!I,7!6IN+'I!+78IQ9LI:;

.y)-r' ,i"u# Gu"ta

&C::--' 'I:I!N


73/107

&C::--' 'I:I!N

As the primary beam pass through the patient,

some of the radiation is absorbed, while the rest

is scattered in many directions

This multidirectional scattered radiation is a

noise factor

In a radiograph of good!uality, less than one-fourthe density should result


74/107

the density should resultfrom scattered radiation.

:I! !% &C::--' :! 7I,; 'I


75/107

It increases with"

increase in the area of the radiation field

and the thic#ness of the part

increase in tube potential

increase in the density of the tissues

Chest 80%scattered 20%primary

Abdomen - 90%scattered 10%primary


76/107

'I!+78IC +I'


77/107

$e/eloped by Gusta/ Buc#y in 0102

It is a de/ice placed between the patient and

the cassette for the purpose of reducing

the amount of scattered radiation reaching thefilm and impro/ing radiographic contrast


78/107

Gusta/ Buc#y3s original gird

+ross hatch type

)odern stationary grid consists of thin , closely


79/107

spaced lead strip measuring about 445mm inwidth

Radiolucent material, plastic or aluminiumseparate them which is 422mm wide

Aluminum is preferred for impro/ed durability of

the grid


80/107

'6N:+-'I&'6N:

+-


81/107

Re!uireIncreas

ede6posure

+astshadowsontheradiographas

thinwhitelines

Absorb147scattered

radiation

-%%ICI-NC; !% 'I!+78IC +I'&


82/107

$epends on

%hysical factors .unctional factors

78;&ICL %C:!&


83/107

0 Grid ratio "- r 8 d9w:d-depth of the interspace channel,

w-width of this channel;


84/107

$epends on"

0 *electi/ity


85/107

Selecti!ity

grid cutoff %rimary radiation transmitted 9scattered radiation transmitted

*#trastIm"r!eme#t 3actr

# 8 Radiographic contrast with grid9Radiographic contrast with out grid

:89,< 9L-


86/107

If Object > 11 Cm Thick Grid is to be used

Grid is to be always used With Intensifyin

!creen

+I'


87/107

Stationary grid

Moving grid

&::I!N; +I'


88/107

Thin wafer grids

Taped to the front of cassette

'sed with intensifying screen

>+R**&$ GRI$= is used in +erebral angiography

*tationary Grid


89/107

Non focused focused

7LL-L ! N!N %!C9&-' +I'


90/107

$istance decentering

'sed in fluoroscopy

7LL-L ! N!N %!C9&-' +I'


91/107

Angulation decentering

%!C9&-' +I'

) f l d


92/107

)ore fre!uently used type

+omprise of parallel strips

*lant more towards lateral edges around a +N?&RG&N+& IN&

'sed in *tanding Abdomen *can, ateral +er/ical

*pine, *wimmers ?iew, %ortable


93/107

,!6IN+ +I'


94/107

$e/eloped by $r (ollis %otter - 01


95/107

%R&+A'TN* IN T(& '*& . .+'*&$ GRI$*


96/107

This sho!d be "ept more #or a c!earerimage to minimise the scattered radiationand a!so the b!rring$

0 *'R+& I)AG& R&+&%TR

$I*TAN+&

n &ocsed grid there ni#orm decrease in densityo# radiograph

n 'on#ocsed grid there is decentering o# beam


97/107

)*C+, . /. &ACT. & 12 1 S .3&3..3 )3C

14 ts e##iciency in c!eaning p scattered radiation$

24 Centering is !ess critica!$

54 6ess e7posre to the patient$4 6ead strips are thic"er there by absorbing more

e##icient!y$

-,!6L !% &C::--' 'I:I!N


98/107

*pace between the patient and the

image receptor is #nown as air gap

Increasing the air gap allows more of the scattered

photons to mo/e laterally outside the film area

$ue to In/erse *!uare aw, there is only small reduction in prima

intensity which can be compensated by increasing the ma

This also result in magnification of image

There is no absorption of scattered radiation in


99/107

the air gap

It re!uire increase in e6posure factors to

#eep radiographic density unchanged

This techni!ue has a place in chest radiograph,

magnification radiograph and in cerebral and

renal angiography

eduction !f &cattered adiation


100/107

Aperture $iaphragms

+ones

+ollimators

7-:9- 'I78+,


101/107

C!N-&


102/107

.AR&$ +N& +IN$&R +N&

C!LLI,:!&


103/107

AN$& (&& &..&+T AN$& +'T ..


104/107

epends on the ang!e the rays ma"e (ith the #ace

o# the targetThe variation in e7posre rate according to the

ang!e o# emission o# the radiation at the #oca! spot

is ca!!ed anode cto## or anode hee! e##ect

Sma!!est e7posre rate occrs at the anode

*se#! in radiographing a region (ith (ide range

o# thic"ness $

Thickest "art is towards the cathode end of the beam

Thinnest "art is towards the anode.


105/107

C!,7-N&:I!N %IL:-&


106/107

Made p o# a!minim or barim p!astic

:ide app!ication in genera! radiography sch as aort arch angiography; Anteropost$ pro


107/107

THA, Y/U

Imaging With X-Rays

Documents

Transcript of Imaging With X-Rays